Free piston engine compressor



A. 5. KING 3,172,596

FREE PISTON ENGINE COMPRESSOR March 9, 1965 Filed Jan. 15, 1962 2 Sheets-Sheet 1 z K 76 A6? /24 Z 1. fl

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March 9, 1965 s. KING 3,172,595

FREE PISTON ENGINE COMPRESSOR Filed Jan. 15, 1962 2 Sheets-Sheet 2 United States Patent "ice? 3,172,596 FREE PISTON ENGINE COMPRESSOR Arthur S. King, 6836 Fontana, Prairie Village, Kans. Filed Jan. 15, 1962, Ser. No. 166,308 9 Claims. (Cl. 230-56) This invention relates to fluid compressors, and more particularly, to an engine compressor of the free-piston type. It is well known to use a two-cycle internal combustion engine in combination with a piston-type compressor for use in refrigeration systems or the like. Heretofore, such engine compressors have been subject to certain characteristic limitations so that their use has not been wide-spread. In addition to certain limitations inherent in conventional two-cycle engines, the increased sealing problems encountered in previous engine compressor assemblies usually resulted in loss of fluid, often expensive refrigerant fluids, from the compressor unit. Additionally, products of combustion have escaped from the cylinder of the engine into the compressor where they contaminated the other fluids.

Accordingly, it is the most important object of my invention to provide an improved engine compressor assembly having means to prevent the loss from the component being contaminated by other fluids leaking into the respective components.

A further important object of this invention is the provision of automatic means for returning to the system any fluid which inadvertently escapes from the compressor unit so that the assembly may be operated with substantially no loss of fluid during the compressing operation while requiring a minimum of operator supervision and maintenance.

Still another object of this invention is the provision of an improved internal combustion engine for use in an engine compressor assembly capable of more efficient operation than with heretofore known engines and adaptable to either gas or carburetor fuels so that operation of the assembly is feasible for a wide range of uses.

Another object of my instant invention is the provision of a free-piston engine compressor assembly utilizing spring means for returning the power piston to top deadcenter position for obviating the use of so-called bounce cylinders and pistons, commonly thought necessary for this purpose, thus avoiding the inevitable problem of fluids leaking past the seals of such bounce cylinders.

A further object of the present invention is the provision for use with such an assembly, of a reciprocating magneto operably coupled with a make-and-break vibrator so that adequate spark is furnished for starting the engine, automatically followed by timed ignition for smooth operation when the engine has started cycling.

Yet another object of this instant invention is the provision of improved lubricating and sealing means for preventing the escape of products of combustion and other fluids from within the combustion chamber to other Fatented Mar. 9, 1965 components of the assembly, thereby insuring mat such waste materials are properly exhausted to the atmosphere to render an internal combustion engine safe for extended operation with very little operator attention.

In the drawings:

FIGURE 1 is a top plan view of the engine compressor assembly embodying the principles of the invention, parts being broken away to reveal details of construction;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1, with the battery, starting button, and fuel pump motor shown schematically; and

FIG. 3 is a fragmentary, cross-sectional view taken along line 3-3 of FIG. 1.

Briefly, this invention relates to a free-piston engine compressor assembly wherein a compressor unit, having a reciprocable compressing member, is operably coupled with the power piston of a two-cycle, free-piston, internal combustion engine by a rigid, reciprocable Work shaft. The engine is provided with a piston pump driven by an electric motor for providing the necessary fuel compression for starting the engine. Starting ignition is initiated by a make-and-break vibration which induces an electrical current in the secondary windings of an induction coil, the latter being operably coupled with a reciprocating magneto to automatically provide timed ignition after the engine has commenced running.

A secondary piston reciprocated by the work shaft forces fuel into the combustion chamber, and a springbiased valve withholds the injection of fuel until a predetermined fuel pressure is reached.

A coil spring is used to return the engine piston to top dead-center position, thus eliminating the need for a conventional bounce piston. Novel means is provided for directing a large volume of compressed air into the cylinder to scavenge the combustion chamber after the fuel supply has been cut off.

A sealed compartment is disposed between the compressor unit and the engine and surrounds the work shaft. The primary purpose of the compartment is to provide a buffer into which any-of the fluid, which may inadvertently escape from the unit during the compressing operation, must leak. The compartment retains the fluids and a valve, disposed in a passage communicating the compartment with the means for conducting fluid into the compressor unit, is automatically operated by the latter to return any escaped fluid to the system.

An engine compressor assembly broadly designated 10, includes a compressor unit 12 and prime mover means for the compressor in the form of a two-cycle internal combustion engine 14. Engine 14 is of the free-piston type and is provided with a cylinder 16 defining a combustion chamber 18 in which is received a power piston 20 for reciprocation in cylinder 16. The latter is closed at one end by head wall 22 and at the opposite end by a relatively thick base plate 24.

Cylinder 16 is provided on the external surface thereof with the conventional fins 26 for cooling engine 14. Piston 20 is provided with a depending, annular skirt 28, and cylinder 16 has an exhaust port 30 communicating the interior of cylinder 16 with the atmosphere. Port 30 is so disposed intermediate the ends of cylinder 16 to be entirely covered by skirt 28 during a portion of the reciprocation of piston 20 within cylinder 16, and to be uncovered by piston 20 when the latter is reciprocated to 3 a position adjacent'plate 24. Seal means 32 circumscribes piston 20 in an annular recess 34 to prevent the flow of fluid between the outer surface of piston 20 and the inner surface of cylinder 16 during the reciprocation of piston 20.

Piston 20 is rigidly coupled with a work shaft 36 extending through plate 24 and into unit 12. Work shaft 36 is rigidly coupled with a member 38 extending in sealing relationship across a. drum 4% defining the compressing chamber of unit 12. The rigid coupling of piston 20 with member 38 by work shaft 36, insures that member 38 will be reciprocated within drum 40 as piston 28 reciprocates. within cylinder 16.

An enclosure 42 in the form of a cylindrical wall, extends between unit 12 and engine 14 and defines a compartment 44 which is generally sealed against ingress or egress of fluid by rigid cou ling to plate 24 and one end 46 of unit 12. Work shaft 36 passes through the compartment 44 and a first seal 48 in plate 24 and disposed in surrounding relationship to work shaft 36, operates to prevent the flow of fluid from engine 14 into compartment 44. To this end, seal 48 includes an annular recess 49 adapted to be filled with liquid in a manner to be made clear hereinafter, and a pair of O-ring seals or the like 51 and 53 disposed in circling relationship with respect to work shaft 36 and on either side of recess 49 in channels provided in plate 24.

A second seal 54 in end 46 and disposed around work shaft 36, prevents the escape of fluid from compressor unit 12 into compartment 44. Inasmuch as work shaft 36 reciprocates during the operation of assembly 10 and compressor unit 12 contains fluid at relatively high pressures, it is difiicult to absolutely prevent the passage of any fluid along reciprocating work shaft 36 and past seal 56. Such leakage, however, is calculated to be received into compartment 44 for a purpose to be hereinafter more fully explained.

Means for delivering fuel into combustion chamber 18 of engine 14, includes a second cylinder 52 within compartment 44 and surrounding work shaft 36. Second cylinder 52 is closed at the upper end thereof by plate 24 and has a transversely extending end wall 54 closing the opposite end.

Work shaft 36 extends through the cavity 56 defined by cylinder 52, and a fluid seal 58 is disposed adjacent wall 54 to prevent the passage of fluid from cavity 56 into compartment 44. A second piston 60 is rigidly secured to work shaft 36 as by key 62 for reciprocation within cylinder 52, and has conventional seal means 64 circumscribing piston 60 to prevent the passage of fluid between piston 60 and between cylinder 52 and piston 60 as the latter is reciprocated by work shaft 36.

A passage 66, extending through plate 24, communicates with cavity 56 and is adapted to be coupled with a source of fuel for engine 14 by extension 68 bolted to the outer surface of plate 24. A check valve 70 is dis posed in extension 68 between the source of fuel and passage 66 to permit the passage of fuel from the source to cavity 56 and to preclude flow in the opposite direction.

A second passage 72 in plate 24, is in fluid communication with cavity 56 and a conduit 74 secured to the outer surface of plate 24 and extending to a tank 76 situated above cylinder 16 and secured to head wall 22 of the latter. A second check valve 78 is disposed adjacent the discharge opening of conduit 74 within tank 76 to permit fluid to flow into the latter and to prevent the return flow thereof from tank 76 in the direction of cavity 56. Control means Si comprising a valve 82 biased by a coil spring 84 into closing disposition across a passage 86 communicating tank 76 with combustion chamber 18 of cylinder 16, prevents the flow of fuel from tank 76 into combustion chamber 18 until the fuel reaches a predetermined pressure.

A cylinder 83 integral with tank 76, and in fluid communication therewith, has a small piston disposed therein to prevent the flow of fluid out of tank 76 through cylinder 88. Piston 91 is operably coupled with an eccentric 92 by piston rod 94 and eccentric 92 is coupled with motor 96 through worm gears 98 whereby rotation of eccentric 92 by motor 96, reciprocates piston 90 within cylinder 88 for a purpose to be explained later.

A coil spring 100 is disposed between the upper surface of plate 24 and the bottom surface of piston 20 to bias the latter toward its top dead-center position after piston 20 has been driven toward a position adjacent plate 24 by the combustion of the fuel within combustion chamber 18.

A liquid-containing vessel 1G2, disposed in surrounding relationship to work shaft 36, and having its bottom end closed by plate 24 and the upper end thereof constricted and provided with a fluid seal 164 in fluid-sealing relationship to reciprocating work shaft 36, communicates with a liquid supply tank 106 positioned outside of cylinder 16. Passage 168 extending through plate 24, provides the means for communicating tank 106 with vessel 102.

Plunger means 110 comprising a piston 112 in tank 196, and a spring 114, urges the liquid within tank 106 through passage 108 and into vessel 192 for a purpose to be later described. A channel 116 extending longitudinally through the upper portion of work shaft 36, is placed in fluid communication with the inside of vessel 102 by laterally extending ports 118 so located in work shaft 36 to be disposed within vessel 162 throughout the entire reciprocation of work shaft 36 during operation of engine 14. Channel 116 communicates with a canal 120 extending radially outwardly in piston 20 and communicating with recess 34 in the outer surface of piston 20. Thus, the urging of the liquid into vessel 102 by plunger means further urges the liquid into channel 116 where it is distributed to recess 34 by canal for the lubricating of the outer surface of piston 20.

The inside of cylinder 16 is placed in fluid communication with the atmosphere by a laterally extending port 122 and an extension 124 provided with a check valve 126 which permits the passage of air into cylinder 16, but prevents the flow of air in the opposite direction. Port 122 is disposed adjacent plate 24 at the bottom of cylinder 16 in a position not to be covered by skirt 28 of piston 20 throughout substantially the entire reciprocation of the latter. Means is provided for conducting the air which enters cylinder 16 beneath piston 20, into the combustion chamber 18 above piston 20. Such means is in the form of a block 128 integral with the outer surface of cylinder 16 and having a passage 130 in fluid communication with the inside of cylinder 16 adjacent plate 24 at a port 132. Passage 130 also communicates with combustion chamber 18 through a port 134 disposed in vertically spaced relationship with respect to plate 24 and in a position to be cleared by piston 20 when the latter is reciprocated to a position adjacent plate 24. Port 134 is disposed in opposed relationship with respect to exhaust port 30, and port 132 is disposed in opposed relationship with air intake port 122.

Additional means for pumping air into cylinder 16, comprises a conduit 136 communicating with second cylinder 52 through an opening 138 in end wall 54, and with air intake port 122 of engine 14. As piston 20 and second piston 60 are reciprocated to their uppermost positions, check valve 126 is opened to permit air to flow into engine 14 through port 122 as will be more fully explained later. Inasmuch as conduit 136 is in fluid communication with port 122, air is sucked into second cylinder 52 by the upward reciprocation of piston 60. Thus, cavity 56 beneath piston 60, is filled with air at the time that the pistons are in their upper positions as illustrated in FIG. 2.

Ignition means for causing the combustion of the fuel within engine 14 comprises a spark plug 140 electrically coupled with means for energizing the same. Such energizing means includes components for energization when L; engine 14 is initially being started and other components for producing timed ignition after engine 14 has started running. The starting components comprise electrically responsive induction apparatus 142 in the form of a conventional make-and-break vibrator having a spring 144 provided with an electrical contact 146 and associated with a vibrator spring 148 having an electrical contact 159.

Spring 144 is electrically coupled with one pole of a suitable source of electrical energy which may be in the form of a battery 152, by line 154 shown in FIG. 2. The other side of battery 152 is electrically coupled with a single-pole single-throw switch 156 by line 158. The other pole of switch 156 is grounded to assembly 10 by line 160 which is connected to an outwardly extending cooling fin 162 which is provided on the outer surface of enclosure 42. The connection between line 160 and fin 162 may be by soldering or the like. Lines 154 and 160 are coupled to motor 96 by lines 164 and 166 respectively to place motor 96 in parallel, electrical connection across battery 152.

Spring 144 of apparatus 142 is insulated from a mounting bolt 143, but spring 148 is electrically coupled with bolt 143. The latter is insulated from enclosure 42 by a block 145 and a washer 147 of insulating material. Bolt 143 is electrically coupled with the primary windings of an induction coil 168 by line 170 and lead 172. Thus, when switch 156 is depressed, a circuit is completed to energize motor 96 traced from battery 152, line 158, switch 156, line 166, motor 96, line 164 to the other side of battery 152. As previously described, one end of induction coil 168 is coupled to lead 172. The other end of the primary windings of coil 168 is electrically coupled with enclosure 42 as by soldering or the like, not shown.

Thus, when switch 156 is closed, a circuit energizing coil 168 may be traced through battery 152, switch 156, line 160, enclosure 42, primary windings of coil 163, lead 172, line 179, bolt 143, spring 14%, contact 15d, contact 146, spring 144, line 154 to the other side of battery 152. An extension 174', integral with the outer end of spring 148, is disposed adjacent a core 176 operably associated with induction coil 16%, whereby extension 174- is attracted toward core 176 as the latter is magnetized through the passage of electricity through the primary windings of coil 168. Contacts 154} and 146 are so disposed in opposing relationship that they are normally connected, but may be separated as core 176 attracts extension 174 of spring 148.

It will be readily understood, of course, that the secondary windings of coil 168 are grounded at one end by connection to closure 42, and the other end thereof is electrically coupled with spark plug 14% by ignition wire 178 shown but fragmentarily in the drawings.

A magneto provides the necessary ignition for the operation of engine 14 after the latter has started cycling. To this end, a permanent magnet 18% is releasably secured to shaft 36 for reciprocation by the latter and may be adjustably positioned at a predetermined location along the longitudinal length of work shaft 36 by setscrew 1322.

Mechanism 184 comprises a fixed contact 136 rigidly mounted in the side wall of enclosure 42 and insulated from the latter by a block 133 of insulating material, is externally threaded and kerfed at one end so that contact 186 may be moved inwardly or outwardly by turning the latter with a screw driver or the like. A generally L-shaped, movable contact 1% is pivotally coupled to a bracket 192 rigidly secured to the inside of enclosure 42 adjacent fixed contact 186, and is biased by spring 154 so that a projection 196 integral with contact 1% is normally in engagement with the inner end of fixed contact 186.

Bracket 192 is constructed of electrically conductive material, as is movable contact 191?, and the pivotal coupling of the latter to bracket 192 permits the electrical connection between the bracket 192 and contact 190 at all times. A leg 198 of contact 199 extends laterally inwardly from the point of pivot of the latter with bracket 192, and is in position to be engaged by permanent magnet 184) as the latter is reciprocated with work shaft 36. A line 200 electrically couples lead 172 with fixed contact 186. Inasmuch as the primary windings of induction coil 168 are grounded to enclosure 42, as previously explained, a closed circuit may be traced from the primary windings through lead 172, line 200, fixed contact 186, projection 196 of movable contact 190, bracket 192, to enclosure 42.

End 4-6 of compressor unit 12 is provided with an annular groove 262 which in turn is in fiuid communication with a conduit 204 shown fragmentarily in FIGS. 1 and 2, which is adapted to be coupled with a source of fluid to be compressed. The fluid from such source is presumed to be at a relatively low pressure and may be a component of a closed refrigerating system or the like. Groove 202 extends through the inner surface of end 46 and communicates with the interior of drum 40. Thus, groove 202 comprises fluid-conductor means for conveying the fluid from conduit 204 to the interior of drum 4%.

An annular plate valve 266 is positioned within drum 40 in surrounding relationship with work shaft 36 and is held in covering relationship to groove 202 adjacent the inner surface of end 46 by spring clips 203. Valve 2% is thus positioned to prevent the flow of fluid from within drum 4%), outwardly into groove 2ti2 and conduit 254, but clips are yieldable to permit the flow of fluid in the opposite direction into drum 4%.

Member 38 is provided with a plurality of transversely extending holes 210 communicating that portion of the interior of drum 4% above member 33 with that portion below the latter. An annular valve plate 212, having a center section 214 secured on work shaft 36 by nut 216 or the like, and outwardly radiating spokes (not shown), is held in closing relationship to holes 210 adjacent the undersurface of member 38. The resiliency of the spokes of plate 212, permits the latter to be shifted away from member 38 under the force of fluid pressure acting on the upper surface of plate 212 to permit the flow of fluid through holes 210 when member 38 is shifted upwardly against fluid contained within the upper portion of drum 4%. Conversely, on the downward stroke of member 38, the force of fluid within the lower portion of drum 4Q, acting against the undersurface of plate 212, holds the latter securely against the undersur face of member 38 to prevent flow of fluid through holes 210.

The bottom of drum 4% is provided with a plurality of holes 21% which are normally closed by an annular plate valve 22% held in place adjacent the undersurface of the bottom of drum 4% by spring clips 222. It will be readily understood that plate valve 220 will permit the flow of fluid downwardly from within drum 40, but will not permit fluid to enter drum .46 from the bottom. Outlet means 224 which may comprise a pan 226 disposed beneath the bottom of drum 4% and a pipe 228 in fluid communication with pan 226 and shown fragmentarily in FIG. 2, is adapted to be coupled with a receptacle for receiving the fluid to be compressed by unit 12 which may be components of a refrigerating system or the like.

A passage 231) extends between compartment 44 and groove 2122 in end 46. A valve 232 biased into closing relationship with passage 230 by spring 234, prevents the flow of fluid from groove 2tl2. into compartment 44.

However, valve 232 may be shifted downwardly against the bias of spring 234 as by suction on the outer face of valve 232, to permit fluid which may be within compartment 44 to be drawn into groove 2112. To this end, valve 232 is of frusto-conical configuration and is complementally engaged on a valve seat around the rim of passage, 239.

In operation, engine 14 is started by manually depressing switch 156- to make electrical connection with motor 96 and the electrically responsive induction apparatus 142. The energizing of motor 96 causes the reciprocation of piston 90 by the eccentric 92. Piston 9b is thus caused to pump fuel which is within tank 76 at all times, downwardly against valve 82 and cause the latter to open against the bias of spring 84, thereby admitting fuel into combustion chamber 18 of engine 14. Simultaneously with the energizing of motor 96, apparatus 142 is energized, and electrical current flows through the primary windings of induction coil 168 from the circuit previously outlined. This current causes the magnetizing of core 176 which attracts extension 174, thus separating contacts 150 and 146. When contacts 150 and 146 are separated, the current through the primary windings of coil 168 is shut off through the breaking of the circuit and core 176 is tie-magnetized. Thus, extension 174 is permitted to return to a position wherein contacts 146 and 150 are again engaged, resulting in magnetizing of core 176. This making-and-breaking of the induction coil circuit is automatically repeated as is quite conventional, so long as switch 156 is closed. The makingand-breaking of the circuit in the primary windings of coil 168, induces a current in the secondary windings of coil 168 which is conveyed to spark plug 140 by wire 178 to cause the igniting of the fuel within the chamber 18 in the well-known, conventional manner for internal combustion engines.

As the fuel within chamber 18 explodes, piston 20 is driven downwardly in cylinder 16. As piston 20 is driven downwardly, the air trapped within cylinder 16 beneath piston 20 is compressed. Check valve 126 remains closed and prevents escape of air from extension 124. Skirt 28, depending downwardly from piston 20, covers exhaust port 38 during this phase of the reciprocation of piston 20 and prevents the escape of air therethrough. After piston 20 has been forced downwardly a predetermined distance, port 30 is uncovered by piston 20, as is port 134 of air passage 130. This permits the air in cylinder 16 to pass through passage 130, port 134, through combustion chamber 18, and out exhaust port 30 to scavenge the products of combustion from chamber 18.

Inasmuch as second piston 60 reciprocates downwardly on shaft 36 with piston 30, the air that is within second cylinder 52 beneath piston 60 is forced into cylinder 16 through conduit 136, thereby increasing the 'volume of air which is forced into combustion chamber 18 through passage 130 when piston 20 uncovers port 134. Such passage of air from beneath piston 60 additionally performs the function of preventing the build-up of air pressure within cylinder 52 which occurs in conventional bounce cylinders in some forms of free-piston engines. Such air pressure build-up is undesirable inasmuch as it presents diflicult fluid sealing problems.

As second piston 60 moves downwardly on the combustion stroke, check valve 70 in extension 68 which is coupled to the source of fuel, opens to admit fuel which is sucked into cavity 56 of cylinder 52.' After piston 20 reaches its bottom position, it is urged upwardly under the bias of spring 180, check valve 70 then closes, and the fuel which was drawn into cavity 56 on the down stroke, is then forced upwardly through passage 72 and conduit 74 into tank 76. Whenever the pressure within the tank 76 is increased to a predetermined amount, calculated to correspond with a certain position of piston 20 within cylinder 16, the bias of spring 84 is overcome by the fuel pressure and valve 82 opens to admit a charge of fuel into combustion chamber 18. Thus, the automatic introduction of fuel into chamber 18 obviates the necessity for continued operation of piston 90 by motor 96, and switch 156 may be released after the initial stroke. 7

The upward movement of piston 20 and work shaft 36 carries permanent magnet 180 past core 176, thereby inducing a current in the primary windings of induction coil 168 as is well known. When piston 20 has reached a predetermined position and it is desired to have the fuel within combustion chamber 18 ignited, permanent magnet contacts movable contact of breaker mechanism 184 to break the flow of current within the primary windings of coil 168. Such breaking induces the current in the secondary windings of coil 168 and such current is carried to spark plug 140 by wire 178 to effect igniting of the fuel. Thus, engine 14 operates automatically after initial starting, and it is not necessary for continued operation of the make-and-break mechanism to eifect firing of the spark plug 140.

Member 38 is reciprocated with work shaft 36 during cycling of engine 14, and on the downward stroke of member 38, whatever fluid is contained below the latter is compressed until suflicient pressure is generated within drum 40 to overcome the bias of spring clips 222 and permit plate valve 220 to open to admit fluid to pass through holes 218 in the bottom of drum 40 and into out let means 224. The pressure of the fluid in outlet means 224 against plate 220, merely serves to hold the latter more firmly in place in covering relationship to holes 218 and precludes the flow of fluid from the outlet to the drum. Additionally, downward movement of member 38 causes plate valve 206 to be shifted away from groove 202 and permit the sucking of fluid from conduit 204 into drum 4%. As member 38 is reciprocated upwardly, the fluid passes through holes 210 and past valve plate 212 into position to be compressed on the next succeeding downward stroke of member 38.

Previous attempts to provide free-piston engine compressor assemblies have not been generally successful, inasmuch as no effective means has been provided to prevent the escape of fluid from the system during the compressing operation. If the assembly is utilized in a refrigerating system, the Freon gases and the like utilized for such systems, are quite expensive. The leaking of the fluid from the system during compressing, not only results in increased operator attention and maintenance on the assembly, but further results in substantial economical loss from the necessity for replacing the refrigerating gases.

Inasmuch as enclosure 42 is sealed to plate 24 and end 46, compartment 44 is disposed to receive any fluids which leak out of drum 40 past seal 50 during compressing operation. Such fluids are entrapped in compartment 44 and, inasmuch as their pressure after escape is greatly reduced, do not have a tendency to seep past the buffer provided by compartment 44 and into any of the other components of engine 14. As member 38 reciprocates downwardly within drum 40, considerable suction is presented in groove 202 to draw the fluid to be compressed from the source. Additionally, this suction acts upon valve 232 to unseat the latter and permit any fluids which are entrapped within compartment 44 to be re-admitted into the compressing unit.

Thus, although every attempt is made to seal against the leaking of fluid past seal 50, it is recognized that inadvertent leakage will place drum 40 in fluid communication with compartment 44. Valve 232, operable as it is by member 38, provides means for automatically retuming the fluid to drum 40 for compressing. Assembly 10 then is capable of operating efliciently over long periods of time with substantially no loss of fluid during the compression operation.

To avoid the possibility of products of combustion, compressed air, or other fluids entering compartment 44 where they might be admitted to the compressing unit, improved sealing means is disposed around shaft 36. Vessel 162 is kept filled with liquid at all times and provides a liquid seal permitting free reciprocation of shaft 36 without the possibility of fluids escaping. The liquid within vessel 102 provides necessary lubrication for shaft 36 and seeps along the latter to fill recess 49. Such liquid, trapped between seals 51 and 53, additionally insures against the seepage of fluid from cylinder 16. With the above described sealing precautions taken against the escape of fluid from engine 14 into compartment 44,

encased assembly is assured of operation without any products of combustion being admitted to a closed refrigerating system or the like.

Although the ignition of the internal combustion engine 14 has been described and explained with the use of a magneto, there is no intention to limit the ignition to such a device. On the contrary, it will be readily understood that other ignition devices could perform suitably for use with engine 14. Among these devices would be included electronic switching systems using a transistor or a thyratron, gated radio frequency systems, or systems using a piezoelectric material as the source of ignition energy.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In an assembly of the kind described, an internal combustion engine having a cylinder and a piston reciprocable in the cylinder:

a compressor spaced from the engine and provided with a drum having a fluid inlet and a fluid outlet;

at fluid compressing member reciprocable in the drum between said inlet and outlet, there being check valve means operably associated with said inlet and outlet for restricting flow of fluid from the inlet to the outlet during reciprocation of the member;

structure presenting a closed compartment independent of the drum and the inlet, located between the cylinder and the drum and including an end for the drum separating the latter from the compartment, said structure being provided with means presenting a single passage only communicating the interior of the compartment with a first area of the drum on the side of the member at the lowest relative pressure within the drum during reciprocation of the member in one direction;

a shaft interconnecting the piston and the member and passing through the compartment and said end for reciprocating the member whereby the only effective entrance for fluid to the compartment is through the end around said shaft; and

check valve mechanism within said passage defining means operable to open and communicate the drum with said compartment only when the pressure in said first area of the drum is lower than the pressure within the drum in a second area thereof on the side of said member opposed to said first area during reciprocation of the member in said one direction whereby fluid which escapes into and is trapped in the compartment may flow therefrom through said passage defining means into said first area of the drum.

2. An assembly as set forth in claim 1, wherein said check valve mechanism includes a valve shiftable in the passage from a closed to an open position, and spring means operably coupled with the valve normally holding the valve in said closed position and yieldable to permit shifting of the valve to said open position When the pressure in said first area of the drum is a predetermined amount less than the pressure in said chamber.

3. An assembly as set forth in claim 1, wherein the inlet extends into said end for the drum, and said passage communicates the inlet with said chamber.

4. An assembly as set forth in claim 1, wherein said passage is disposed to communicate the interior of the compartment with that area of the drum on the side of the member at the lowest relative pressure within the drum during reciprocation of the member in a direction to efiect compression of the fluid therein.

5. In an assembly of the kind described, an internal combustion engine having a cylinder and a piston reciprocable in the cylinder and provided with sealing means between the cylinder and the piston; a compressor spaced from the engine and provided with a drum having a fluid inlet and a fluid outlet; a fluid compressing member reciprocable in the drum, said inlet and said outlet each having means for restricting flow of fluid from the inlet to the outlet during reciprocation of the member; structure presenting a compartment between the cylinder and the drum, including a wall for the cylinder separating the latter from the compartment; a shaft interconnecting the piston and the member and passing through the compartment and said wall for reciprocating the'member; and means for preventing escape of products of combustion from the cylinder into the compartment around the shaft through said wall, including a fluid pressure system in the cylinder directed through the shaft and the piston to hold the sealing means tightly against the cylinder.

6. In an assembly of the kind described, an internal combustion engine having a cylinder and a piston reciprocable in the cylinder and provided with sealing means between the cylinder and the piston; a compressor spaced from the engine and provided with a drum having a fluid inlet and a fluid outlet; a fluid compressing member reciprocable in the drum, said inlet and said outlet each having a check valve for restricting flow of fluid from the inlet to the outlet during reciprocation of the member; structure presenting a compartment between the cylinder and the drum, including an end for the drum separating the latter from the compartment and a wall for the cylinder separating the latter from the compartment; a shaft interconnecting the piston and the member and passing through the compartment and said end for reciprocating the member, there being a passage in said end placing the compartment into communication with said compressor for return to the latter of fluid that escapes from the drum into the compartment around the shaft through said end; a check valve in the passage for preventing flow of fluid from the compressor to the compartment; and means for preventing escape of products of combustion from the cylinder into the compartment around the shaft through said wall, including a fluid pressure system in the cylinder directed through the shaft and the piston to hold the sealing means tightly against the cylinder.

7. In an assembly of the kind described, an internal combustion engine having a first cylinder and a first piston reciprocable in the first cylinder; a compressor spaced from the engine and provided with a drum having a fluid inlet and a fluid outlet; a fluid compressing member reciprocable in the drum, said iniet and said outlet each having means for restricting flow of fluid from the inlet to the outlet during reciprocation of the member; structure presenting a compartment between the first cylinder and the drum, including a wall for the first cylinder separating the latter from the compartment; a second cylinder in the compartment having said wall closing one end thereof; a second piston in the second cylinder; a shaft interconnecting the pistons and the member and passing through the cylinders, the compartment and said wall for reciprocating the second piston and the member; and means for preventing escape of products of combustion from the first cylinder into the compartment around the shaft through said wall, including structure responsive to reciprocation of the second piston for feeding fuel to the first cylinder, and structure responsive to reciprocation of the second piston for forcing products out of the first cylinder.

8. A fluid compressor unit comprising a drum closed at opposed ends thereof; a member reciprocable in the drum and extending thereacross in fluid sealing relationship with the side wall of the same, said member having at least one hole extending therethrough; first valve means carried by the member and disposed to permit passage of fluid through the hole when the member is reciprocated in one direction and to preclude such passage when the member is reciprocated in the opposite direction; a work shaft coupled with the member and extending out of the drum through one end of the latter; prime mover means having a compartment communicating with the drum and operably coupled with the work shaft for reciprocating the member; fluid conductor means communicating with the drum and adapted to be coupled with a source of fluid at relatively low pressure; second valve means disposed to preclude the flow of fluid from said conductor means when the member is reciprocated in said one direction and to permit such flow when the member isreciprocated in the opposite direction; outlet means communicating with the drum on the opposite side of the member from said second valve means; third valve means disposed to permit flow of fluid from the drum to the outlet in only one direction and after the fluid has reached a predetermined pressure; and valve means operable by the member for returning to the conductor means any fluid which escapes from the drum into the chamber of said prime mover whereby substantially no fluid is lost during the compressing operation.

9. Apparatus as set forth in claim 8, wherein said conductor means is provided with a passage communicating with said prime mover, and said returning valve means ineludes a pressure responsive valve disposed in said passage to permit fluid flow therethrough only in the direction from the prime mover to the conductor means.

References Cited in the file of this patent UNITED STATES PATENTS 1,950,063 Pescara Mar. 6, 1934 2,038,442 Pescara Apr. 21, 1936 2,241,957 'Pescara May 13, 1941 2,936,743 Colgate May 17, 1960 FOREIGN PATENTS 1,206,240 France Feb. 8, 1960 

1. IN AN ASSEMBLY OF THE KIND DESCRIBED, AN INTERNAL COMBUSTION ENGINE HAVING A CYLINDER AND A PISTON RECIPROCABLE IN THE CYLINDER; A COMPRESSOR SPACED FROM THE ENGINE AND PROVIDED WITH A DRUM HAVING A FLUID INLET AND A FLUID OUTLET; A FLUID COMPRESSING MEMBER RECIPROCABLE IN THE DRUM BETWEEN SAID INLET AND OUTLET, THERE BEING CHECK VALVE MEANS OPERABLY ASSOCIATED WITH SID INLET AND OUTLET FOR RESTRICTING FLOW OF FLUID FROM THE INLET TO THE OUTLET DURING RECIPROCATION OF THE MEMBER; STRUCTURE PRESENTING A CLOSED COMPARTMENT INDEPENDENT OF THE DRUM AND THE INLET, LOCATED BETWEEN THE CYLINDER AND THE DRUM AND INCLUDING AN END FOR THE DRUM SEPARATING THE LATTER FROM THE COMPARTMENT, SAID STRUCTURE BEING PROVIDED WITH MEANS PRESENTING A SINGLE PASSAGE ONLY COMMUNICATING THE INTERIOR OF THE COMPARTMENT WITH A FIRST AREA OF THE DRUM ON THE SIDE OF THE MEMBER AT THE LOWES RELATIVE PRESSURE WITHIN THE DRUM DURING RECIPROCATION OF THE MEMBER IN ONE DIRECTION A SHAFT CONNECTING THE PISTON AND THE MEMBER AND PASSING THROUGH THE COMPARTMENT AND SAID END FOR RECIPROCATING THE MEMBER WHEREBY THE ONLY EFFECTIVE ENTRANCE FOR FLUID TO THE COMPARTMENT IS THROUGH THE END AROUND SAID SHAFT; AND CHECK VALVE MECHANISM WITHIN SAID PASSAGE DEFINING MEANS OPERABLE TO OPEN AND COMMUNICATE THE DRUM WITH SAID COMPARTMENT ONLY WHEN THE PRESSURE IN SAID FIRST AREA OF THE DRUM IS LOWER THAN THE PRESSURE WITHIN THE DRUM IN A SECOND AREA THEREOF ON THE SIDE OF SAID MEMBER OPPOSED TO SADID FIRST AREA DURING RECIPROCATION OF THE MEMBER IN SAID ONE DIRECTION WHEREBY FLUID WHICH ESCAPES INTO AND IS TRAPPED IN THE COMPARTMENT MAY FLOW THEREFROM THROUGH SAID PASSAGE DEFINING MEANS INTO SAID FIRSTE AREA OF THE DRUM. 